TWI767309B - Manufacturing method for silicon carbide ingot and system for manufacturing silicon carbide ingot - Google Patents

Abstract

The present invention relates to a method for producing a silicon carbide ingot and a system for producing a silicon carbide ingot, wherein, in the process of producing the silicon carbide ingot, in the step of actually growing the ingot, the heating unit is moved at a predetermined speed by moving the heating unit. , to change the temperature distribution inside the reaction vessel according to the growth of the ingot.

Description

Manufacturing method of silicon carbide ingot and system for manufacturing silicon carbide crystal ingot

The present invention relates to a method for manufacturing a silicon carbide crystal ingot and a system for manufacturing the silicon carbide crystal ingot.

Silicon carbide has attracted attention as a semiconductor material because it has excellent heat resistance and mechanical strength, and is physically and chemically stable. Recently, the demand for silicon carbide single crystal substrates is increasing as substrates for high power devices and the like.

As the preparation method of silicon carbide single crystal, there are liquid phase epitaxy (LPE), chemical vapor deposition (Chemical Vapor Deposition, CVD), physical vapor transport (Physical Vapor Transport, PVT) and the like. Among them, in the physical vapor transport method, the silicon carbide raw material is put into the crucible, the seed crystal formed by the silicon carbide single crystal is placed on the upper end of the crucible, and then the crucible is heated by induction heating to sublime the raw material, so as to grow on the seed crystal Silicon carbide single crystal.

The physical vapor transport method is the most widely used due to its high growth rate and the ability to prepare silicon carbide in the form of ingots. However, during the induction heating of the crucible, the temperature distribution inside the crucible changes according to the temperature gradient conditions, the relative positions of the heating units, and the temperature difference between the upper and lower parts of the crucible, thus possibly affecting the quality of the manufactured silicon carbide ingot .

Therefore, in order to improve the crystal quality of the silicon carbide ingot and ensure the reproducibility of manufacturing the ingot, it is necessary to fully consider the factors that may affect the temperature distribution inside the crucible during the growth step.

The above-mentioned prior art is the technical information possessed by the inventor for the derivation of the present invention or obtained during the derivation process, so it is not necessarily a known technology disclosed to the public before the application of the present invention.

As a related prior art, there is "a large-diameter single crystal growth apparatus and a growth method using the same" disclosed in Korean Laid-Open Patent Publication No. 10-2013-0124023.

An object of the present invention is to provide a method for manufacturing a silicon carbide ingot and a system for manufacturing a silicon carbide ingot. Movement at a predetermined speed changes the temperature distribution inside the reaction vessel according to the growth of the ingot.

An object of the present invention is to provide a method of manufacturing a silicon carbide ingot, which minimizes the height deviation between the center and the edge of the silicon carbide ingot and improves the crystal quality.

In order to achieve the above purpose, a method for manufacturing a silicon carbide ingot according to an embodiment includes: a preparation step of adjusting the inner space of a reaction vessel in which the silicon carbide raw material and seed crystals are placed into a high vacuum atmosphere, and performing the step of injecting an inert gas into the The inner space is heated by a heating unit surrounding the reaction vessel to sublimate the silicon carbide raw material, thereby inducing the growth of a silicon carbide ingot on the seed crystal, and a cooling step to cool the temperature of the inner space to a temperature of the chamber temperature; the performing step includes a process of moving the heating unit; the heating unit moves so that the relative position based on the seed crystal is away from the seed crystal at a speed of 0.1 mm/hour to 0.48 mm/hour.

In one embodiment, the performing step includes a pre-growth process and a growth process in sequence; the pre-growth process sequentially includes: a first process of changing the high vacuum atmosphere in the preparation step to an inert atmosphere; a second process, Using the heating unit to increase the temperature of the inner space, and a third process of reducing the pressure of the inner space to reach the growth pressure, and raising the temperature so that the temperature of the inner space becomes the growth temperature; the growth process Is the process of maintaining the inner space at the growth temperature and the growth pressure and inducing the growth of the ingot, and the movement of the heating unit may be performed during the growth process.

In one embodiment, the maximum heating area is an area corresponding to a position of the center of the heating unit in the inner space, and the temperature of the maximum heating area may be 2100°C to 2500°C.

In one embodiment, the inner space has a secondary heating area, the temperature of the secondary heating area is 110°C to 160°C lower than the temperature of the maximum heating area, and the heating unit can move to maintain the secondary heating temperature of the area.

In one embodiment, the temperature difference is the difference between the temperature of the upper part of the inner space and the temperature of the lower part of the inner space, and the temperature difference may be 40°C to 60°C in the first process.

In one embodiment, the total moving distance of the heating unit may be more than 10 mm.

In one embodiment, the temperature difference is the difference between the temperature of the upper part of the inner space and the temperature of the lower part of the inner space, the temperature difference during the growth process may be different than the temperature difference during the first process Maximum 70°C to 120°C.

In one embodiment, the silicon carbide ingot is based on the back surface, and the difference between the height of the center and the edge of the front surface as the opposite surface is 0.01mm to 3mm, and the maximum height in the direction perpendicular to the back surface can be 15mm or more.

In one embodiment, the micropipe density of the silicon carbide ingot can be below 1/cm ² , the basal plane dislocation density can be below 1300/cm ² , and the etch pit density can be below 12000/cm ² .

In order to achieve the above-mentioned purpose, in the silicon carbide ingot of one embodiment, the difference between the height of the center of the front surface and the height of the edge of the opposite surface is 0.01 mm to 3 mm, and the maximum height in the direction perpendicular to the back surface is based on the back surface. is 15 mm or more, the micropipe density can be 1/cm ² or less, the basal plane dislocation density can be 1300/cm ² or less, and the etching pit density can be 12000/cm ² or less.

In order to achieve the above object, a system for manufacturing a silicon carbide ingot according to an embodiment includes: a reaction vessel having an inner space, a heat insulating material disposed on the outer surface of the reaction vessel to surround the reaction vessel, and a heating unit, For adjusting the temperature of the reaction vessel or the inner space; the silicon carbide seed crystal is located in the upper part of the inner space, and the raw material is located in the lower part of the inner space; including a moving unit for changing the heating unit and the the relative position between the reaction vessels in the vertical direction; growing a silicon carbide ingot from the seed crystal; moving the heating unit so that the relative position based on the seed crystal is 0.1 mm/hour to 0.48 mm /hour away from the seed crystals.

In one embodiment, the maximum heating area is an area corresponding to the central position of the heating unit in the inner space, and based on the maximum heating area, the temperature of the heating unit when moving may be 2100°C to 2100°C. 2500 ° C; the auxiliary heating area is located in the upper part of the inner space; the auxiliary heating area is the inner area of the heating unit, and the inner area is based on any line connecting the silicon carbide raw material and the seed crystal, from the heating unit. Both ends have a prescribed length toward the center; the temperature of the secondary heating region may be 110°C to 160°C lower than the temperature of the maximum heating region.

In one embodiment, the silicon carbide ingot is based on the back surface, and the difference between the height of the center and the edge of the front surface as the opposite surface is 0.01mm to 3mm, and the maximum height in the direction perpendicular to the back surface can be 15mm or more.

In one embodiment, the micropipe density of the silicon carbide ingot can be below 1/cm ² , the basal plane dislocation density can be below 1300/cm ² , and the etch pit density can be below 12000/cm ² .

A method of manufacturing a silicon carbide ingot, a system for manufacturing a silicon carbide ingot, and the like according to an embodiment, by adjusting the relative positions of the reaction vessel and the heating unit at a predetermined speed in the growth step of the silicon carbide ingot, so that the manufactured The height deviation between the center and the edge of the silicon carbide ingot is minimized and the crystal quality is improved.

The advantage of the silicon carbide ingot of an embodiment is that the defect density of micropipes, basal plane dislocations, etching pits, etc. is low, and cracks or polymorphs are almost generated.

Hereinafter, the embodiments are described in detail with reference to the accompanying drawings, so that those skilled in the art to which the present invention pertains can easily implement the present invention. However, the embodiments of the present invention can be implemented in various embodiments, and are not limited to the embodiments described in this specification. Throughout the specification, the same drawing reference numerals are attached to similar parts.

In this specification, unless otherwise stated, when a certain structure "includes" another structure, it means that other structures are also included but not excluded.

In this specification, when a certain structure is "connected" to another structure, this includes not only the case of "direct connection" but also the case of "connected by connecting other structures therebetween".

In this specification, B on A means that B is directly in contact with A or B is on A in the case where another layer is provided between B and A, and cannot be interpreted limitedly as B is in contact with the surface of A.

In this specification, the term "their combination" included in the Markush-form expression means a mixture or combination of one or more selected from the group consisting of a plurality of structural elements described in the Markush-form expression, and means One or more selected from the group consisting of the plurality of structural elements are included.

In this specification, the description of "A and/or B" means "A or B or A and B".

In this specification, unless stated otherwise, terms such as "first", "second" or "A", "B" are used to distinguish the same terms.

In this specification, unless a different meaning is clearly indicated in the sentence, the expression of the singular includes the expression of the plural.

While researching a method for minimizing the occurrence of defects and cracks in a silicon carbide ingot and improving the crystal quality, the inventors have invented a method for manufacturing a silicon carbide ingot, which can be used in the growth step of the silicon carbide ingot to specify The velocity changes the relative positions of the reaction vessel and the heating unit, and examples are provided.

Manufacturing method of silicon carbide ingot

In order to achieve the above-mentioned purpose, a method for manufacturing a silicon carbide ingot according to an embodiment includes: preparing step Sa, adjusting the inner space of the reaction vessel 200 where the silicon carbide raw material 300 and the seed crystal 110 are placed into a high vacuum atmosphere, and performing steps Sb, S1 , injecting an inert gas into the inner space, and raising the temperature through the heating unit 600 surrounding the reaction vessel to sublimate the silicon carbide raw material, thereby inducing the growth of silicon carbide ingot 100 on the seed crystal, and cooling step S2, cooling the temperature of the inner space to room temperature; the performing step includes a process of moving the heating unit, and the heating unit is moved so that the relative position based on the seed crystal is 0.1 mm/hour to A speed of 0.48 mm/hr away from the seed crystal.

The heating unit 600 and the reaction vessel 200 may be installed to be able to change relative positions in a vertical direction. The relative position may be changed by the moving unit, and may be changed by moving any one or more of the heating unit and the reaction vessel. Compared with the movement of the position of the reaction vessel, changing the relative position by the movement of the heating unit is beneficial to the growth of a stable silicon carbide ingot.

1 , 4 and 5 show examples of manufacturing equipment of silicon carbide ingots. The manufacturing method of the silicon carbide ingot of the embodiment will be described with reference to this.

The preparation step Sa is a step of arranging the raw material 300 and the silicon carbide seed crystal 110 to face each other in the reaction vessel 200 having an inner space and adjusting the atmosphere to a high vacuum.

In the preparation step Sa, the pressure of the inner space can be reduced to 50 Torr or less, 10 Torr or less, or 5 Torr or less, and can be reduced to 1 Torr or more. When going through such a high vacuum atmosphere preparation step, a defect-reduced ingot can be produced.

The silicon carbide seed crystal 110 in the preparation step Sa can be appropriately sized according to the target ingot, for example, a silicon carbide wafer can be used. And the C-plane ((000-1) plane) of the silicon carbide seed crystal may face the raw material 300 .

The silicon carbide seed crystal 110 in the preparation step Sa may include 4H silicon carbide with a size of more than 4 inches, and may also include 4H silicon carbide with a size of more than 6 inches.

When the silicon carbide seed crystal 110 is in the form of attachment to a seed crystal holder (not shown), the silicon carbide seed crystal may also include an adhesive layer placed on the backside. When the silicon carbide seed crystal is in a form not directly attached to the seed crystal support, the silicon carbide seed crystal may also include a protective layer disposed on the backside. In this case, the growth of silicon carbide ingots with fewer defects can be induced.

The silicon carbide raw material 300 of the preparation step Sa may be used in a powder shape having a carbon source and a silicon source, and the raw material may include silicon carbide powder.

The silicon carbide raw material 300 may include silicon carbide powders necked with each other or silicon carbide powders obtained by carbonizing their surfaces. In this case, more efficient SiC growth can be aided by inducing more stable SiC sublimation during growth.

The reaction vessel 200 in the preparation step Sa may be a vessel suitable for the growth reaction of silicon carbide ingots, and specifically, a graphite crucible may be used. For example, the reaction vessel may include a body 210 having an inner space and an opening, and a lid 220 corresponding to the opening to close the inner space. The crucible cover may further include a seed crystal holder formed integrally with the crucible cover or formed separately, and the silicon carbide seed crystal may be fixed by the seed crystal holder, so that the silicon carbide seed crystal 110 and the silicon carbide raw material 300 face each other. .

The reaction vessel 200 of the preparation step Sa may include a heat insulating material 400 placed on the outer surface to surround the reaction vessel, and the heat insulating material may be in contact with the reaction vessel or have a prescribed distance. A heat insulating material surrounding the reaction vessel may be located in the reaction chamber 500 such as a quartz tube, and the temperature of the inner space of the reaction vessel 200 and the like may be controlled by the heat insulating material and a heating unit 600 disposed outside the reaction chamber .

The porosity of the heat insulating material 400 in the preparation step Sa may be 72% to 95%, 75% to 93%, or 80% to 91%. When a heat insulating material satisfying the porosity is used, the generation of cracks in the grown silicon carbide ingot can be further reduced.

The heat insulating material 400 in the preparation step Sa may have a compressive strength of 0.2 MPa or more, 0.48 MPa, or 0.8 MPa or more. In addition, the compressive strength of the heat insulating material may be 3 MPa or less, or 2.5 MPa or less. When the heat insulating material has such compressive strength, it is excellent in thermal/mechanical stability, and the occurrence probability of ash is reduced, so that a silicon carbide ingot of better quality can be produced.

The heat insulating material 400 in the preparation step Sa may include carbon-based felt, specifically, may include graphite felt, rayon-based graphite felt or pitch-based graphite felt.

The reaction chamber 500 may include: a vacuum exhaust device 700 connected to the interior of the reaction chamber for adjusting the vacuum degree inside the reaction chamber; a pipeline 810 connected to the interior of the reaction chamber for introducing gas into the reaction chamber inside the reaction chamber; and, a mass flow controller 800 for gas control. Through these, the flow rate of the inert gas can be adjusted in the subsequent growth step and cooling step.

In the performing steps Sb and S1, inert gas is injected into the inner space and the raw material is sublimated by adjusting the temperature, pressure and atmosphere of the inner space, thereby inducing SiC on the SiC seed crystal 110 Ingot 100 grows.

In the performing steps Sb, S1, the inner space may be substantially changed to an inert gas atmosphere. The inert gas atmosphere can be formed by, after the process of placing the silicon carbide raw material 300 and the seed crystal 110 and the like, depressurizing the inner space of the reaction vessel under the atmospheric atmosphere and inducing it to be substantially a vacuum atmosphere and then injecting the inert gas , but not limited to this.

The inert gas atmosphere in the steps Sb and S1 refers to that the atmosphere of the inner space in the growth step is not the atmospheric atmosphere, but also includes such a situation: although the inert gas atmosphere is mainly used, in order to realize the doping of silicon carbide crystals. A small amount of gas is injected for the purpose of the ingot. The inert gas atmosphere is suitable for inert gas, which can be, for example, argon gas, helium gas or a mixture thereof.

The performing steps Sb and S1 may be performed by heating the reaction vessel 200 or the inner space of the reaction vessel by the heating unit 600 , or, the degree of vacuum may be adjusted by decompressing the inner space at the same time or in addition to the heating. , and inject inert gas.

The performing steps Sb and S1 induce the sublimation of the silicon carbide raw material 300 and the growth of the silicon carbide ingot 100 on a surface of the silicon carbide seed crystal 110 .

The heating unit 600 may be placed around the reaction vessel 200 to be mounted to be movable in a vertical direction substantially parallel to any line from the silicon carbide seed 110 to the feedstock 300, and may include A moving unit that changes the relative position in the vertical direction between the heating unit and the reaction vessel. Therefore, the relative position between the reaction vessel and the heating unit can be changed, and a temperature gradient in the inner space can be induced. In particular, the heating unit may impose a temperature difference between the upper portion 230 of the inner space and the lower portion 240 of the inner space.

The heating unit 600 may be applicable to an induction heating unit formed as a spiral coil along the outer peripheral surface of the reaction vessel 200 or the heat insulating material 400 surrounding the reaction vessel, but is not limited thereto.

The performing steps Sb and S1 may sequentially include a pre-growth process Sb and a growth process S1, and the pre-growth process may sequentially include: a first process Sb1, changing the high vacuum atmosphere in the preparation step to an inert atmosphere, and a second process. Process Sb2, using the heating unit 600 to increase the temperature of the inner space, and third process Sb3, reducing the pressure of the inner space to reach the growth pressure, and raising the temperature so that the temperature of the inner space becomes the growth temperature .

The growth process S1 is a process of maintaining the inner space at the growth temperature and the growth pressure and inducing the induced ingot to grow.

The first process Sb1 can be performed by injecting an inert gas such as argon. At this time, the pressure of the inner space may be 500 Torr to 800 Torr.

The second process Sb2 is a process of heating the lower portion 240 of the inner space to a pre-growth start temperature of 1500°C to 1700°C. The temperature increase in the second process Sb2 may be performed at a rate of 1°C/min to 10°C/min.

In the third process Sb3, the lower portion 240 of the inner space may be heated up to a growth temperature of 2100°C to 2500°C, and decompressed to a growth pressure of 1 Torr to 50 Torr. The temperature increase in the third process Sb3 may be performed at a rate of 1°C/min to 5°C/min.

Within the range of the temperature increase rate and pressure of the second process and the third process, the occurrence of polymorphisms other than the target crystal can be prevented, and stable growth can be induced.

5 , the upper portion 230 of the inner space is an area of the inner space close to the surface of the silicon carbide seed crystal 110 or ingot, and the lower portion 240 of the inner space is an area of the inner space close to the surface of the raw material 300 . Specifically, the upper portion 230 of the interior space is about 5 mm or more below the surface of the silicon carbide seed or ingot, and more specifically, the temperature measured at a location of about 5 mm, and the lower portion 240 of the interior space is at The temperature measured at a position of about 10 mm above the surface of the raw material 300, more specifically, at a position of about 10 mm. When the upper portion of the inner space or the lower portion of the inner space is at the same position when viewed from the longitudinal direction of the crucible, and if the temperature measured at each measurement position is different, the temperature of the central portion is used as a reference.

The growth process S1 may include a process of moving the relative position of the heating unit with the reaction vessel as a reference.

The meaning of maintaining the growth pressure in the growth process S1 includes the case where the pressure of the inflow gas is slightly adjusted as necessary within the range where the growth of the silicon carbide ingot is not stopped under the reduced pressure. In addition, the meaning of maintaining the growth pressure means that the pressure of the inner space is maintained within a predetermined range within a range capable of maintaining the growth of the silicon carbide ingot.

The pre-growth process Sb may apply a prescribed temperature difference to the upper portion 230 of the inner space and the lower portion 240 of the inner space, and the temperature difference in the pre-growth start temperature may be 40°C to 60°C, or 50°C to 55°C. The temperature difference in the growth temperature may be 110°C to 160°C, or 135°C to 150°C. By having the temperature difference as described above, the generation of polymorphisms other than the target crystal can be prevented when the initial silicon carbide ingot is formed, and the ingot can be stably grown.

The heating rate of the third process Sb3 may be lower than the average heating rate of the entire second process Sb2 and the third process Sb3. The overall average temperature increase temperature of the second process and the third process is a value obtained by dividing the difference between the temperature at the temperature increase start time point of the second process and the temperature at the end time point of the third process by the elapsed time , the heating rate in the third process refers to the heating rate at each time point in the third process.

The heating unit 600 may have a maximum heating area, and the maximum heating area refers to the highest temperature portion of the atmosphere of the inner space heated by the heating unit. When the heating unit surrounds the side surface of the reaction vessel in the form of a spiral coil, the inner space corresponding to the center of the heating unit is a maximum heating area. For example, when it is assumed that a vertical line (vertical center line) connecting the centers of the silicon carbide raw material 300 and the seed crystal 110 and a surface extending in the horizontal direction from the center of the height of the heating unit (heating unit center surface), the The maximum heating area may be the area where the intersection between the vertical centerline and the horizontal plane of the heating unit is located.

In the second process Sb1 and the third process Sb2, the maximum heating area of the heating unit can be the lower part of the reaction vessel, that is, the surface 240 of the raw material, and when the heating unit has a spiral coil shape, it can be The number and thickness of coils are varied to apply the targeted temperature difference between the upper and lower parts of the interior space.

In the growth process S1, after the temperature is raised to the growth temperature in the third process Sb3, the raw material is formally sublimated to form a silicon carbide ingot. At this time, the growth temperature may be maintained to form a silicon carbide ingot. The meaning of maintaining the growth temperature does not necessarily mean that it must be carried out at a fixed proceeding temperature, but means that even if the absolute temperature changes slightly, the silicon carbide grows within a range where the temperature change is not sufficient to stop the growth of the silicon carbide ingot.

In the growth process S1, the heating unit moves so that the relative position with the seed crystal as a reference is away from the seed crystal at a speed of 0.1 mm/hour to 0.48 mm/hour. The relative position may be moved away at a speed of 0.1 mm/hour to 0.4 mm/hour based on the seed crystal 110, or may be moved away at a speed of 0.2 mm/hour to 0.3 mm/hour. The speed range is a relatively low speed range, and when the relative position is changed at the speed as described above, it is possible to prevent the formation of polymorphisms other than the target crystal in the grown silicon carbide ingot, and it is possible to manufacture a silicon carbide ingot with a relatively low speed. Defect-less silicon carbide ingots.

In the growth process S1, the change of the relative position of the heating unit 600 relative to the reaction vessel 200 and the seed crystal 110 may be performed after reaching the growth temperature, or may be performed 1 hour to 10 hours after reaching the growth temperature .

In the growth process S1 , the upper portion 230 of the inner space may have a sub-heating region whose temperature is 110° C. to 160° C. lower than that of the largest heating region in the reaction vessel. The temperature of the secondary heating zone may be 135°C to 150°C lower than the temperature of the maximum heating zone.

The sub-heating region refers to a portion where the temperature is relatively low in the atmosphere of the inner space heated by the heating unit. When the heating unit surrounds the side surface of the reaction vessel in the form of a spiral coil, the secondary heating area may be located above the maximum heating area.

Assuming a vertical line (vertical center line) connecting the centers of the silicon carbide raw material 300 and the seed crystal 110 and a surface extending in the horizontal direction from the center of the height of the heating unit (heating unit center surface), the sub heating area It may be a region between the maximum heating region and the surface of the silicon carbide seed crystal or ingot, and preferably, at least a part of the sub-heating region may overlap an upper portion of the inner space.

The heating unit 600 can be moved in a vertical direction based on the reaction vessel through a moving unit, and the moving unit is used to change the relative position between the heating unit and the reaction vessel 200 in the vertical direction. That is, with reference to any line from the seed crystal 110 placed in the reaction vessel to the silicon carbide raw material 300 , it can move in a direction substantially juxtaposed.

The heating unit 600 of the growth process S1 may descend and move at the speed based on the reaction vessel.

Based on the maximum heating area, the growth temperature in the growth process S1 may be 2100°C to 2500°C, or 2200°C to 2400°C. In addition, based on the upper portion 230 of the inner space, the temperature during the growth process may be 1900°C to 2300°C, or 2100°C to 2250°C.

During the growth process S1, the total moving distance of the heating unit may be 10 mm or more, or 15 mm or more. The total moving distance may be 45 mm or less, or 30 mm or less.

The growth process S1 may be performed for 5 hours to 200 hours, and may also be performed for 75 hours to 100 hours.

In the pre-growth process Sb and/or the growth process S1, the reaction vessel 200 is rotated with the vertical direction as the axis, which can induce the formation of a more favorable temperature gradient for the growth of the silicon carbide ingot.

The steps Sb and S1 may be performed by adding a predetermined flow of inert gas to the outside of the reaction vessel 200 . The inert gas may form a gas flow in the inner space of the reaction vessel 200, and may induce a gas flow in the direction from the raw material material 300 to the silicon carbide seed crystal. Therefore, a stable temperature gradient of the reaction vessel and the inner space can be formed.

The cooling step S2 is a step of cooling the silicon carbide ingot grown by the performing step under the conditions of a predetermined cooling rate and an inert gas flow rate.

In the cooling step S2, cooling may be performed at a rate of 1°C/min to 10°C/min, or cooling may be performed at a rate of 1°C/min to 5°C/min.

In the cooling step S2, the pressure adjustment of the inner space of the reaction vessel 200 may be performed simultaneously with the cooling step, or the pressure adjustment may be performed separately. The pressure can be adjusted to a maximum of 800 Torr in the interior space.

In the cooling step S2, as in the performing step, a predetermined flow rate of an inert gas may be applied to the inside of the reaction vessel 200. The inert gas may flow in the inner space of the reaction vessel, and the flow may be formed in a direction from the raw material material 300 to the silicon carbide seed crystal 110 .

The cooling step S2 may include: a first cooling process, pressurizing so that the pressure of the inner space of the reaction vessel 200 is higher than atmospheric pressure, and cooling so that the temperature of the inner space is 1500° C. to 1,700° C. based on the upper part 230 °C; a second cooling step, after the first cooling step, the temperature of the inner space is cooled to room temperature.

The recovery of the cooling step S2 may be performed by cutting the backside of the silicon carbide ingot in contact with the seed crystal 110 . The cut silicon carbide ingot exhibits a good height difference between the center and edge of the grown end and can have a reduced defect density. The specific shape and defect density of the silicon carbide ingot will be described below.

System for manufacturing silicon carbide ingots

In order to achieve the above object, a system for manufacturing a silicon carbide ingot of one embodiment includes a reaction vessel 200 having an inner space, a thermal insulating material 400 disposed on an outer surface of the reaction vessel to surround the reaction vessel, and The heating unit 600 is used to control the temperature of the reaction vessel or the inner space; the silicon carbide seed crystal 110 is located in the upper part of the inner space, and the raw material 300 is located in the lower part of the inner space; and a moving unit is included for changing the temperature of the inner space. the relative position in the vertical direction between the heating unit and the reaction vessel; growing a silicon carbide ingot from the seed crystal; through the movement of the heating unit, the heating unit moves so that the seed crystal is The relative position of the reference is away from the seed crystal at a speed of 0.1 mm/hour to 0.48 mm/hour.

The silicon carbide ingot 100 is based on the back surface separated from the silicon carbide seed crystal 110, and the difference between the height of the center and the edge of the front surface as the opposite surface is 0.01mm to 3mm, and the height perpendicular to the back surface is 0.01mm to 3mm. The maximum height of the direction may be 15mm or more.

The micropipe density of the silicon carbide ingot 100 may be less than 1/cm ² , the basal plane dislocation density may be less than 1300/cm ² , and the etch pit density may be 12000/cm ² or less.

4 , the reaction vessel 200 may include a body 210 having an inner space and an opening, and a lid 220 corresponding to the opening to form the inner space, and other matters are the same as those described above.

The material and physical properties of the heat insulating material 400 are the same as those described above.

The system for manufacturing a silicon carbide ingot may include a reaction chamber 500 in which a reaction vessel 200 surrounded by a thermal insulating material 400 is placed. In this case, the heating unit 600 may be disposed outside the reaction chamber to control the temperature of the inner space of the reaction vessel.

The reaction chamber 500 may include: a vacuum exhaust device 700 connected to the interior of the reaction chamber for adjusting the degree of vacuum inside the reaction chamber; a pipe 810 connected to the interior of the reaction chamber for introducing gas into the reaction chamber inside the reaction chamber; and a mass flow controller 800 for gas control. Through these, the flow rate of the inert gas can be adjusted in the growth step and the cooling step.

The heating unit 600, referring to FIG. 5 , the relative position of the heating unit relative to the reaction vessel 200 can be separated at a speed of 0.1mm/hour to 0.48mm/hour, or 0.1mm/hour to 0.4mm/hour. The speed of the hour is far away, and it can also be moved away at a speed of 0.2mm/hour to 0.3mm/hour. When the above-mentioned moving speed is satisfied, even if the ingot grows and the position of the surface changes, a stable temperature difference and temperature gradient can be applied, and the formation of polycrystals other than the target crystal can be prevented.

The movement of the heating unit 600 may be performed in the performing step of subliming the raw material and preparing the silicon carbide ingot grown from the seed crystal by adjusting the temperature, pressure and atmosphere of the inner space, for example, may be performed as the performing step The second process, the third process and the growth process of the pre-growth process are performed, and these steps and processes are the same as those described above.

A moving unit is included for changing the relative position between the heating unit 600 and the reaction vessel 200 in the vertical direction, and in the growth step, the speed can be lowered as shown in FIG. move.

The heating unit 600 may allow the maximum heating area to be located in the lower part of the inner space. The maximum heating area is the area of the inner space located at a position corresponding to the center of the heating unit. When the heating unit is in the shape of a helical coil, the inner area of the heating unit having a predetermined length from the center of the heating unit to both ends may be the maximum based on any line connecting the silicon carbide raw material and the seed crystal 110 heating area. The temperature of the maximum heating zone may be 2100°C to 2500°C, or 2200°C to 2400°C.

The heating unit 600 can be moved so that the temperature of the upper portion 230 of the inner space is 110°C to 160°C lower than the temperature of the maximum heating area, and also 135°C to 150°C lower in the growth step. When the heating unit is in the shape of a helical coil, the upper part of the inner space may be located above the maximum heating area, that is, the center. The temperature of the upper part of the inner space may be 1900°C to 2300°C, or 2100°C to 2250°C.

The system for manufacturing a silicon carbide ingot may sequentially perform the above-mentioned preparation step Sa, performing steps Sb, S1, cooling step S2, and the like.

Silicon carbide ingot

In order to achieve the above-mentioned purpose, in the silicon carbide ingot 100 of an embodiment, when the back side cut from the silicon carbide seed crystal 110 is used as a reference, the difference between the height of the front center and the edge height as the opposite side can be 0.01mm to 3mm, or 0.01mm to 2.9mm.

The maximum height of the silicon carbide ingot 100 in the direction perpendicular to the back surface may be 15 mm or more, 18 mm or more, or 21.6 mm or more.

The micropipe density of the silicon carbide ingot 100 may be 1/cm ² or less, 0.8/cm ² or less, or 0.59/cm ² or less.

The basal plane dislocation density of the silicon carbide ingot 100 may be 1300/cm ² or less, 1100/cm ² or less, or 980/cm ² or less.

The etch pit density of the silicon carbide ingot 100 may be 12,000/cm ² or less, or 10,000/cm ² or less.

After preparing the wafer by cutting the silicon carbide ingot 100, and immersing it in molten potassium hydroxide (KOH) at 500°C for 5 minutes to etch the wafer, the wafer is measured by an optical microscope or the like. Defects per unit area of the surface, allowing calculation of micropipe, basal plane dislocation and etch pit density.

The silicon carbide ingot 100 is made to satisfy the above-mentioned defect density range to provide a wafer with few defects, and when applied to a device, a device having excellent electrical or optical characteristics can be manufactured.

Hereinafter, the present invention will be further specifically described through specific examples. The following examples are only examples for helping understanding of the present invention, and the scope of the present invention is not limited thereto.

< Example - Manufacture of Silicon Carbide Ingots >

As an example of the silicon carbide ingot manufacturing equipment shown in FIGS. 4 and 5 , silicon carbide powder as a raw material 300 is charged into the lower part 240 of the inner space of the reaction vessel 200 , and a silicon carbide seed crystal is placed in the upper part 230 of the inner space. At this time, a silicon carbide seed crystal composed of a 6-inch 4H silicon carbide crystal was used and fixed by a conventional method so that the C-plane ((000-1) plane) faced the silicon carbide raw material in the lower part of the inner space.

After sealing the reaction vessel 200 and surrounding its outside with a heat insulating material 400, the reaction vessel was set in a quartz tube 500 having a heating coil as a heating unit 600 on the outside.

As shown in FIG. 1 , the inner space of the reaction vessel 200 was depressurized to adjust to a vacuum atmosphere, and argon gas was injected to make the inner space reach 760 Torr, and the temperature of the inner space was based on the lower part The rate of 10°C/min was increased to 1600°C. Next, as a pre-growth process, the temperature was increased at a rate of 3° C./min while depressurizing, and the temperature of the lower part of the inner space was set to 2350° C. of the temperature of the maximum heating region of the heating unit. Then, while maintaining the same conditions, a silicon carbide ingot was grown under the conditions of the moving speed, time, and moving distance of the heating unit shown in Table 1.

After the growth, the temperature of the inner space was cooled to 25° C. at a rate of 5° C./min, while argon gas was injected so that the pressure of the inner space became 760 Torr. Then, the formed silicon carbide ingot is cut to separate from the seed crystal.

< Comparative example - Change the moving speed of the heating unit >

In the above-described embodiment, the same manner as in the above-described embodiment was performed except that the moving speed, time, and moving distance of the heating unit were changed to the conditions of Table 1.

< Experimental example - Measure the height, height difference and the presence of cracks of the prepared silicon carbide ingot >

The front surface of the silicon carbide ingot prepared in each of the examples and the comparative example, the height of the center of the front surface of the growth end was measured with an altimeter, the height of the periphery of the silicon carbide ingot was measured, and the cut as the ingot was visually inspected Table 1 shows the results of cracks in the seed plane of the plane.

< Experimental example - Defect density measurement of wafers >

The silicon carbide ingots of the respective Examples and Comparative Examples were cut to have an off-angle of 4° with the seed plane as the cut plane, and wafer samples having a thickness of 360 μm were prepared.

The dicing was carried out with a size of 50 mm x 50 mm in an area having an outer diameter of 95% compared to the maximum outer diameter of the wafer sample. It is immersed in molten potassium hydroxide (KOH) at 500° C. for 5 minutes and etched, and defects on its surface are photographed by an optical microscope or the like. The shell-shaped pits are classified as basal plane dislocations (BPDs) and the black giant hexagonal perforated pits are classified as microtubules (MPs).

The 500 μm×500 μm area in the diced wafer sample was randomly designated 12 times, the number of defects in each area was determined, and the average number of defects per unit area was calculated to obtain the defect density. The results are shown in Table 1.

Ingot height difference*: The difference between the center height and the edge height of the front side of the opposite side based on the back side of the ingot MP*: Micropipe, Micropipe BPD*: Basal Plane Dislocation EPD*: Etch Pit, Etch Pit Density

Referring to Table 1, in the examples in which the moving speed of the heating unit is 0.1 mm/hour to 0.48 mm/hour, the center height of the front surface, which is the opposite surface, is 20 mm based on the back surface of the ingot (the front surface of the seed crystal). The above, and the difference between the height of the center and the edge is 2 mm to 3 mm, and the defect density value of the wafer made of the ingot is also good.

In the comparative example where the heating unit did not move or the moving speed was 0.5 mm/hour, the center height was 11 mm or less, and in the comparative example 1, cracks were generated on the back side (seed crystal front side) of the ingot, and the ingot was made of The defect density value of the wafer is relatively high.

The preferred embodiments of the present invention have been described in detail above, but the scope of the rights of the present invention is not limited thereto. Those skilled in the art to which the present invention pertains can implement various modifications and improvements using the basic concept of the present invention defined by the claims. Forms also fall within the scope of rights of the present invention.

100: Silicon carbide ingot 110: Silicon carbide seed/seed 200: Reaction Vessel 210: Ontology 220: Cover 230: Upper/upper part of interior space 240: Lower part of interior space/surface of raw material 300: Raw Materials / Raw Materials 400: Thermal Insulation 500: Reaction chamber/quartz tube 600: Heating unit 700: Vacuum exhaust 800: Mass Flow Controller 810: Pipes S1: Proceed to step/growth process S2: Cooling step Sa: preparation steps Sb: Perform step/pre-growth process Sb1: The first process Sb2: Second Process Sb3: The third process

FIG. 1 is a conceptual diagram showing an example of a manufacturing apparatus to which the manufacturing method of a silicon carbide ingot according to the present invention is applied. 2 is a graph showing trends of temperature, pressure, and argon gas pressure with respect to time in a method of manufacturing a silicon carbide ingot according to the present invention. 3 is a conceptual diagram showing an ingot manufactured by the method for manufacturing a silicon carbide ingot according to the present invention and a height difference of the front surface of the ingot. 4 is a conceptual diagram showing an example of a manufacturing apparatus of a silicon carbide ingot according to the present invention. FIG. 5 is a conceptual diagram showing a part of a manufacturing facility of a silicon carbide ingot according to the present invention.

S1: Proceed to step/growth process

S2: Cooling step

Sa: preparation steps

Sb: Perform step/pre-growth process

Sb1: The first process

Sb2: Second Process

Sb3: The third process

Claims (10)

A method for manufacturing a silicon carbide crystal ingot, comprising: a preparation step of adjusting an inner space of a reaction vessel in which a silicon carbide raw material and a seed crystal are placed into a high vacuum atmosphere; a step of injecting an inert gas into the inner space, and passing the surrounding The heating unit of the reaction vessel is heated to sublimate the silicon carbide raw material, thereby inducing the growth of a silicon carbide ingot on the seed crystal; and a cooling step, cooling the temperature of the inner space to room temperature, the performing step Including the process of moving the heating unit, the heating unit moves so that the relative position with the seed crystal as a reference is away from the seed crystal at a speed of 0.1 mm/hour to 0.4 mm/hour. The method for manufacturing a silicon carbide ingot according to claim 1, wherein the performing step includes a pre-growth process and a growth process in sequence, and the pre-growth process sequentially includes: a first process, wherein the The high vacuum atmosphere is changed to an inert atmosphere; the second process, the heating unit is used to increase the temperature of the inner space; and the third process, the pressure of the inner space is reduced to reach the growth pressure, and the temperature is raised to make the inner space the temperature of the space reaches a growth temperature, and the growth process is a process of maintaining the inner space at the growth temperature and the growth pressure and inducing the growth of the silicon carbide ingot, The movement of the heating unit is performed during the growth process. The method for manufacturing a silicon carbide ingot according to claim 2, wherein a maximum heating region is a region corresponding to a position of the center of the heating unit in the inner space, and the maximum heating region has a temperature of 2100° C. to 2500℃. The method for producing a silicon carbide ingot according to claim 3, wherein the inner space has a sub-heating region, and the temperature of the sub-heating region is 110°C to 160°C lower than the temperature of the maximum heating region, The heating unit moves to maintain the temperature of the secondary heating area. The method for manufacturing a silicon carbide ingot according to claim 2, wherein the temperature difference is the difference between the temperature of the upper part of the inner space and the temperature of the lower part of the inner space, and the temperature difference in the first process is 40°C to 60°C. The method for manufacturing a silicon carbide ingot according to claim 1, wherein a total moving distance of the heating unit is 10 mm or more. The method of manufacturing a silicon carbide ingot according to claim 2, wherein the temperature difference is a difference between the temperature of the upper part of the inner space and the temperature of the lower part of the inner space, and the temperature difference during the growth is higher than The temperature difference in the first process is as large as 70°C to 120°C. A silicon carbide ingot manufactured by the method for manufacturing a silicon carbide ingot according to any one of claims 1 to 7, comprising a front face and a back face as its opposite face, the back face being a face cut from a seed crystal , based on the back side, the difference between the height of the center of the front side and the height of the edge is 0.01mm to 3mm, and the maximum height in the direction perpendicular to the back side is 15mm or more, and the density of micropipes is 1/cm ² or less , the basal plane dislocation density is 1300/cm ² or less, and the etching pit density is 12000/cm ² or less. A system for manufacturing a silicon carbide ingot, comprising: a reaction vessel having an interior space; a heat insulating material disposed on an outer surface of the reaction vessel to surround the reaction vessel; and a heating unit for conditioning the reaction vessel Or the temperature of the inner space, the silicon carbide seed crystal is located in the upper part of the inner space, the raw material is located in the lower part of the inner space, and the heating unit includes a moving unit for changing the relationship between the heating unit and the reaction vessel. the relative position in the vertical direction between the two, so that the silicon carbide ingot is grown from the seed crystal; the heating unit is moved so that the relative position based on the seed crystal is at a speed of 0.1mm/hour to 0.4mm/hour away from the seed crystals. The system for manufacturing a silicon carbide ingot as claimed in claim 9, wherein the maximum heating area is an area in the inner space corresponding to the position of the center of the heating unit, based on the maximum heating area, The temperature of the heating unit when moving is 2100°C to 2500°C, the sub-heating area is located in the upper part of the inner space, and the temperature of the sub-heating area is 110°C to 160°C lower than the temperature of the maximum heating area temperature.

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